To stabilize the egg whites you need to add 1/4 teaspoon cream of tartar. I beat 4 egg whites with 1/4 teaspoon cream of tartar and 1/2 teaspoon vanilla until the egg whites reach soft peak. Then add 6 tablespoon of sugar a little at a time and continue beating until the egg white become stiff and glossy. Cream of tartar can also be used when making quiche to help keep it light and fluffy.